The global asphalt market is to reach 118.4 million metric tons by 2015, according to a January 2011 report by Global Industry Analysts, Inc. The asphalt paving industry accounts for the largest end-use market segment of asphalt. With increasing growth in the developing markets of China, India, and Eastern Europe, asphalt will be increasingly needed to construct roadway infrastructure for the next decade. The increased demand for asphalt, along with the need for improved asphalt materials/pavement performance, creates the opportunity for an asphalt modifier.
The grade of the asphalt governs the performance of paving mixtures at in-service temperatures. In many cases, the characteristics of bitumen needs to be altered to improve its elastic recovery/ductility at low temperatures for sufficient cracking resistance as well as to increase its shearing resistance for sustained loads and/or at high temperatures for rutting resistance. Thus, to provide durable pavements, polymer modifiers are added to confer the desired physical properties to the asphalt. Typical polymer modifiers used include a suspended semicrystalline solid (e.g., polyethylene) or a dispersed SBS-type thermoplastic elastomer (e.g., various SBS products of the Kraton® family).
Over the past decade, there has been increased use of recycled tire rubber in asphalt binders as an alternative to polymer modifiers in the asphalt paving industry due to its good performance and competitive economic opportunity. The use of ground tire rubber (GTR) as an asphalt modifier is an environmentally sustainable mean of enhancing the pavement quality while recycling vast quantities of waste material. Asphalt rubber (AR) binders have being applied since the 1960s. However, the production and storage of the AR presents some challenges. It is important to have the rubber particles evenly distributed in the asphalt matrix for the asphalt rubber. Because the rubber in the GTR is crosslinked, it does not melt completely in asphalt at the blending and production temperatures commonly used. Thus, the AR binders require higher mix and compaction temperatures than the conventional binders. Also, the AR binders typically have some degree of separation during storage due to the immiscibility of the GTR with the asphalt and the disparity in the specific gravities. To increase the asphalt rubber's performance and maintain the storage stability of the rubber after being reacted in asphalt, stabilizers/compatibilizers have been commonly used to swell the rubber particles and form either physical or chemical linkages between the GTR filler particle and asphalt binder.
There are several stabilizers in the market for asphalt rubbers. For example, an additive widely used in the production of AR to reduce mix and compaction temperatures and to prevent separation is polyoctanamer (often referred to as Vestenamer®, Evonik Industries/Degussa). However, the conventional binders are expensive and do not provide environmental benefits. With the forecast of increasing demand of asphalt pavement and AR binders for the next decade, there remains a strong need for new types of cost-effective, environment-friendly, viable polymers that can be used as AR binders in lieu of standard asphalt-rubber binders.
Adhesives are materials that can be fluid, semi-fluid, or materials that can become fluid with external assistance such as heating (e.g., hot-melt adhesives). When applied between two objects, the solidification of the adhesives stick the objects together. The adhesive industry is divided into the packaging industry with a 37% share of the total market, the construction industry with a 20% share (e.g., carpet laying, roofing, pre-finished panels, etc.), the automobile industry with a 19% share, the laminates industry with a 12% share (e.g., labelling, veneers, laminates), the footwear industry with a 5% share, the consumer industry with a 4% share, and other markets constituting the remaining 3% share.
The global market for adhesives in 2013 was estimated by the Adhesive and Sealant Council to be $40.5 billion in sales (approximately 9000 kilo tons) and is expected to reach $58 billion in sales by 2018 (approximately 12,400 kilo tons). There thus remains a strong need in the art for new types of cost-effective, environment-friendly, viable polymers that can be used as adhesives.
“Fracking”, or hydraulic fracturing, is a process for natural gas, petroleum, or uranium solution-extraction from deep formations of shale. The process involves the fracturing of shale rock deposits by a pressurized liquid. The fracking liquid is a mixture of water, sand, and other chemical additives. The typical recipe for fracking fluids consists of 90% water, 8-9% sand, and 1-2% other chemicals such as biocides, acids, inhibitors, stabilizers, crosslinkers, friction reducers, pH adjusting agents, iron control, surfactants, and gelling agents. Because fracking can consume millions of gallons of fracking fluids, 1-2% of the fracking fluids (i.e., 1-2% chemicals among the fracking fluids) can still amount to hundreds of tons. This can be very toxic for the soil and can attribute to deep water well contamination. There is thus a need in the art to develop a polymer as a substitute for the gelling agents such as guar gum, that can serve as a thickening agent for water, as a crosslinking agent, as a pH adjusting agent, as a breaking agent, and as a biocide.
Polymers based on glycerol have been used in the past decade in the fabrication of matrices for drug delivery, scaffolds in tissue engineering, plus many other applications. Similar chemistries have been applied to sorbitol to make polymers. For example, Liu et al, “Preparation and characterization of a thermoplastic poly(glycerol sebacate) elastomer by two-step method,” Journal of Applied Polymer Science 103(3):1412-19 (2007), synthesized a thermoplastic elastomer prepared using poly(glycerol-sebacate) and sebacic acid in a two-step method. Cai et al., “Shape-memory effect of poly (glycerol-sebacate) elastomer,” Materials Letters 62(14):2171-73 (2008), were able to synthesize a poly(glycerol-sebacate) elastomer with excellent shape-memory capabilities.
However, these past efforts have been focusing on acid/alcohol condensation chemistry between glycerol or sorbitol monomer and another monomer. None of them have explored the biopolymers based on polymerization of a polyol monomer or its derivatives. There is thus a need in the art to use a monomer derived from an inexpensive natural biofeedstocks or petrochemical feedstocks to develop a highly processable thermoplastic and elastomeric polymer with a wide range of applications and physical properties.
The present invention is directed to fulfilling these needs in the art.